# Django 2.0.dev20170216164632 documentation

# Source code for django.conf.urls

    from importlib import import_module

    from django.core.exceptions import ImproperlyConfigured
    from django.urls import (
        LocaleRegexURLResolver, RegexURLPattern, RegexURLResolver,
    )
    from django.views import defaults

    __all__ = ['handler400', 'handler403', 'handler404', 'handler500', 'include', 'url']

    handler400 = defaults.bad_request
    handler403 = defaults.permission_denied
    handler404 = defaults.page_not_found
    handler500 = defaults.server_error

    def include(arg, namespace=None):
        app_name = None
        if isinstance(arg, tuple):
            # callable returning a namespace hint
            try:
                urlconf_module, app_name = arg
            except ValueError:
                if namespace:
                    raise ImproperlyConfigured(
                        'Cannot override the namespace for a dynamic module that '
                        'provides a namespace.'
                    )
                raise ImproperlyConfigured(
                    'Passing a %d-tuple to django.conf.urls.include() is not supported. '
                    'Pass a 2-tuple containing the list of patterns and app_name, '
                    'and provide the namespace argument to include() instead.' % len(arg)
                )
        else:
            # No namespace hint - use manually provided namespace
            urlconf_module = arg

        if isinstance(urlconf_module, str):
            urlconf_module = import_module(urlconf_module)
        patterns = getattr(urlconf_module, 'urlpatterns', urlconf_module)
        app_name = getattr(urlconf_module, 'app_name', app_name)
        if namespace and not app_name:
            raise ImproperlyConfigured(
                'Specifying a namespace in django.conf.urls.include() without '
                'providing an app_name is not supported. Set the app_name attribute '
                'in the included module, or pass a 2-tuple containing the list of '
                'patterns and app_name instead.',
            )

        namespace = namespace or app_name

        # Make sure we can iterate through the patterns (without this, some
        # testcases will break).
        if isinstance(patterns, (list, tuple)):
            for url_pattern in patterns:
                # Test if the LocaleRegexURLResolver is used within the include;
                # this should throw an error since this is not allowed!
                if isinstance(url_pattern, LocaleRegexURLResolver):
                    raise ImproperlyConfigured(
                        'Using i18n_patterns in an included URLconf is not allowed.')

        return (urlconf_module, app_name, namespace)

    def url(regex, view, kwargs=None, name=None):
        if isinstance(view, (list, tuple)):
            # For include(...) processing.
            urlconf_module, app_name, namespace = view
            return RegexURLResolver(regex, urlconf_module, kwargs, app_name=app_name, namespace=namespace)
        elif callable(view):
            return RegexURLPattern(regex, view, kwargs, name)
        else:
            raise TypeError('view must be a callable or a list/tuple in the case of include().')